Which cogeneration system description fits best with the following? "A gas turbine compressor supplies pressurized combustion air which is burned in a boiler, producing steam that drives a steam turbine connected to a generator."

The description provided aligns best with a Combined-cycle Steam/Gas Turbine system. In this configuration, a gas turbine generates power by using combustion air that is pressurized by its compressor. The exhaust heat from the gas turbine is typically harnessed to produce steam in a heat recovery steam generator (HRSG) or a boiler. This steam is then used to drive a steam turbine that is also connected to a generator, allowing for the recovery and utilization of waste heat from the gas turbine's operation. This dual approach maximizes the efficiency of the system by combining the two separate cycles - the gas cycle of the gas turbine and the steam cycle of the steam turbine.

In contrast, other options do not capture the complete system as described. A back pressure turbine utilizes steam at lower pressures for mechanical drive and does not incorporate gas turbines in the way described. Waste heat systems focus on the recovery of exhaust energy to generate electrical power but do not depict the full integration described with a gas turbine supplying combustion air and subsequently producing steam for a steam turbine. Gas turbines alone refer specifically to systems operated solely on gas fuel without the context of combined cycles involving steam. Therefore, the combined-cycle steam/gas turbine definition encompasses the complete process outlined in the question.